This invention relates to novel 9-amino-3-keto-11,12-carbazate or carbamate derivatives of 6-O-methylerythromycin A. The compounds of this invention are useful as antibiotic agents in mammals, including man, as well as in fish and birds. The compounds of the present invention are broad-spectrum macrolide antibiotics that are effective against infections caused by certain gram-positive and gram-negative bacteria as well as protozoa. Various derivatives of erythromycin A useful as antibiotic agents are referred to in U.S. patent application Ser. No. 60/049,349, filed Jun. 11, 1997, and U.S. patent application Ser. No. 60/046,150, filed May 9, 1997, both of which are incorporated herein by reference in their entirety.